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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 29, No 2, March/April 2018
AFRICA
107
the economic hub of the country with well-developed intra-city,
inter-city and trans-African highway routes for easy mass transit
of people, goods and services across geographical barriers,
18
making road transportation and the transportation business
important features of its economy. Therefore many companies
engage in long-distance transportation, with professional drivers
employed to provide this service.
In Nigeria there are few studies on the CVD risk profile of
this important but vulnerable group. These studies show that
long-distance drivers have a significant burden of hypertension
and overweight/obesity, comparable to or even higher than
in the general population.
19-21
Hypertension is a common and
important CVD risk factor. Its prevalence among long-distance
bus drivers in Nigeria is 22.5%,
19
which was also the pooled
prevalence of hypertension in the general population in 2012.
22
However, none of these studies screened the drivers for diabetes/
abnormal glucose profiles or dyslipidaemia.
Considering the potential risk associated with professional
driving, the importance of bus drivers to the country’s
socio-economic development and the paucity of data on the
cardiovascular risk profile of long-distance bus drivers, it became
necessary to investigate the prevalence of cardiometabolic and
lifestyle-related risk factors for CVD and their predictors in this
segment of the Nigerian working population in Lagos, south-
west Nigeria. The findings from this study will also help create
awareness of their risk burden and possibly help shape policies
to address this risk.
Methods
This was a cross-sectional study involving male long-distance bus
drivers in major motor parks in Lagos. The parks were selected
based on their size and the routes they serve. Long-distance
driving was defined as a distance of 160-km radius from the
terminal of departure.
23
The calculated sample size was 268 based on the prevalence
of hypertension in the general population.
22
To allow for 15%
attrition rate, the sample size was increased to 308. However, 15
of the drivers did not have complete data and were not included
in the data analysis, giving a response rate of 95%. Therefore
293 was the final sample size used in the data analysis. Ethical
approval for the study was obtained from the Health Research
Ethics Committee of the Lagos University Teaching Hospital.
We used a stratified cluster-sampling method to recruit long-
distance drivers registered with the Transport Workers’ Union
from selected motor parks in Lagos between March and July
2015. The motor parks were then stratified based on whether or
not they organised mandatory annual health and safety training
for their drivers (AHS motor parks). Only two motor parks
employing 400 drivers met this criterion. The drivers in the
AHS motor parks only operate from their company terminals.
We selected one of these for inclusion in the study because its
annual health and safety programme coincided with the study
period. All 168 drivers agreed to participate but three (1.8%)
later declined.
The second category of (non-AHS) motor parks comprised
independent drivers and drivers working for small transport
companies that operate from general and less regulated motor
parks in Lagos and who do not routinely receive formal health
and safety checks. We divided these motor parks into two;
those serving the northern and southern parts of the country,
respectively. We then randomly selected two motor parks from
each of these strata for inclusion in the study, thereby selecting
four in total. Finally, we used a convenience sample of 50 drivers
from each of these four parks and recruited 143 of them (71.5%
response rate). Those who declined did so due to time constraints
and undisclosed personal reasons. Fig. 1 shows the consort
diagram on how the participants were recruited.
On a mutually agreed day, the consenting drivers were
approached in groups and were given a talk on the importance
of healthy living and they were also briefed on the usefulness of
the study. They were told to observe an overnight fast on the day
of the medical screening. We used a structured questionnaire
administered by trained interviewers to obtain their socio-
demographic data and relevant medical history. Those who
couldn’t read or write were assisted to complete the questionnaire
by interviewers who could speak their native languages.
Thereafter their body weights were measured in kilograms
with an Omron HN289 (Osaka, Japan) digital weighing scale,
placed on a firm, flat ground, with participants wearing light
clothing and with no footwear or cap. Measurements were taken
to the nearest 0.5 kg, after ensuring that the scale was always at
the zero mark.
Their heights were measured in centimetres with a Seca
model 216 (GmbH, Hamburg, Germany) stadiometer with the
participant standing erect, back against the height metre rule
and occiput and heels making contact with the height metre rule.
BMI was calculated as weight in kilograms divided by height
squared in metres.
24
BMI was categorised as underweight
<
18.0
kg/m
2
; normal weight 18.0–24.9 kg/m
2
; overweight 25.0–29.9 kg/
m
2
; class I obesity 30.0–34.9 kg/m
2
; class II obesity 35.0–39.9 kg/
m
2
and class III obesity
>
40.0 kg/m
2
.
Participants’ waist circumferences were measured with an
inextensible, inelastic 1-cm-wide tape snug around the body at
the level of the midpoint between the lower margin of the last
palpable rib and the top of the anterior iliac crest. Measurements
were taken at the end of normal respiration and
≥
102 cm was
regarded as abdominal obesity.
25
Their neck circumferences were
also measured with an inextensible, inelastic 1-cm-wide tape at
the level of the cricoid cartilage. A neck circumference
≥
40 cm
defined obesity.
26
The blood pressure (BP) of the participants was measured
by the research assistants after five minutes of rest, with the
participant seated comfortably, feet on the floor, arm at the level of
the heart and free of any constricting clothing. Appropriate-sized
cuffs and bladder connected to an Omron HEM7233 (Osaka,
Japan) digital sphygmomanometer were used in measuring the
BP, which was taken initially on both arms, and the arm with
the higher value was used in subsequent measurements. Three
BP readings were taken at two- to three-minute intervals. The
average of three readings was taken for analysis. Hypertension
was defined as BP
≥
140/90 mmHg, self-volunteered history of
hypertension and/or use of anti-hypertensives.
Venepuncture was done on each participant while observing
aseptic techniques. Five millilitres of venous blood was put in
fluoride oxalate and lithium heparin vacutainer specimen bottles
for fasting plasma glucose and fasting lipid profiles, respectively,
and sent to the laboratory for processing and analysis with a
Beckman (Pasadena, CA, USA) automated clinical chemistry
autoanalyser using standard reagents/kits from Randox